This invention is generally directed to improved developer compositions, and more specifically the present invention is directed to single component color toner compositions containing superparamagnetic polymers. The single component toner compositions of the present invention in one embodiment contain resin particles, pigment and/or colorant particles and a low optical density superparamagnetic polymer. These highly transparent color magnetic toner compositions are useful for developing color images, and in particular for obtaining color highlight images in magnetic imaging systems.
Colored developer compositions comprised of resin particles, carrier particles, and pigments consisting of magenta, cyan, and/or yellow materials are well known, reference for example, U.S. Pat. No. 4,066,563. There is disclosed in this patent color developing compositions containing certain specific cyan, magenta and yellow pigments, which developer compositions when employed together with specific carrier materials are found to be highly useful in developing color images. The intensity of the color desired is dependent not only on the concentrations of the pigments selected but on other factors, including the carrier material selected and the specific composition of the pigment added to the toner resin. Thus, for example, certain types of yellow pigments when used with magenta and cyan pigments result in colored images containing a certain yellow intensity, for example, the yellow might be classified as a light yellow as compared to a bright yellow. Similarly, when certain red pigments are selected for incorporation into the toner composition, there can result developed images of low or high red intensity, that is the red color can change from light red or pink to a deep red in some instances.
These known developer compositions can be selected for developing colored images in xerographic imaging devices especially those referred to in the art as electrostatic imaging systems. In these systems, separate electrostatic latent images are developed in sequence with a developer composition containing for example, a magenta pigment, followed by development with a developer composition containing a yellow pigment, followed by development with a developer composition containing a cyan pigment. The resulting images are then transferred to a suitable support surface and permanently affixed thereon. These systems can be complex in that they require the superimposition of images with three separate exposures, on an imaging member of sufficient circumference or length to accommodate three successive images prior to transfer. Also, it is known to use in such systems a series of three separate inregister photoreceptor drums, each contributing one image to the final transfer sheet, however, such a system is costly, can result in images of poor resolution in view of the complexity of the system and the ned for three separate photoreceptor drums.
In the simpler known functional color imaging systems, generally only two colors need to be reproduced, although more than two can be obtained if desired. For example, in these systems, there is produced two color functional color documents wherein for example, black may be used to represent the main text and red or blue selected portions of the text, figures and like, which portions are directed to a users special attention by means of highlight color. In such systems, there can be obtained images in two colors such as red and black, desirably employing only one imaging operation. In many instances, full color copying is not desired since, for example, the documents being copied such as accounting documents and other business documents, contain colors of black and red only, in addition to white background. Illustrative examples of documents that may be selected for the highlight color process include technical journals such as Scientific American, a large portion of whose spaces are printed in black, and highlight color, engineering drawings, letters, reports, and a variety of other documents created by color ink, crayon, signature impression stamps, typewritter ribbons, and the like. These imaging systems are electrostatic and not magnetic in nature.
There is described in U.S. Pat. No. 4,189,224 a method to obtain a two color image with only a single exposure. More specifically, there is disclosed in this Patent a two color electrostatic copying apparatus which can be operable for one color positive or negative copy. In accordance with the teachings of this patent, a photoconductive material containing a conductive substrate, an inner photoconductive layer sensitive to visible light, and an outer photoconductive layer insensitive to red light, is subjected to an electrostatic charge, which charge is applied to the outer layer, while simultaneously irradiating the device with light so as to render one of the layers conductive. Subsequently, an electrostatic charge of opposite polarity is applied to the outer layer of the photoresponsive member, this step being accomplished in the dark. A light image of an original document is then projected onto the outer layer of the photoresponsive device where white areas of the image cause photoconduction of both layers and the red areas result in photoconduction of only the inner layer. Accordingly, as a result, white areas of material have zero surface potential, while red and black areas have non-zero surface potential of opposite polarities. These images can then be developed by selecting, for example, red and black toner particles of opposite charge.
Also, there is disclosed in U.S. Pat. No. 2,864,333 single component developer compositions, that is, those that do not contain carrier particles. In this patent there is described the use of a magnetic brush system to apply toner particles formed of ferrites and a resin material to an image bearing material, wherein the image contained thereon is developed. Difficulty is encountered with this process in that the conductivity of the resulting toner particles renders electrostatic transfer difficult. However, these processes have been used commercially, wherein special papers such as coated zinc oxide papers are used. Single component toner compositions are also disclosed in U.S. Pat. No. 3,639,245. Additionally there is disclosed in U.S. Pat. No. 4,108,706 a magnetic toner containing specific parameters, while U.S. Pat. No. 4,145,300 discloses developers containing magnetic particles and certain types of dyes, and U.S. Pat. No. 4,146,494, describes single component powders which have incorporated therein finely divided water insoluble quaternary ammonium salts.
Further, there is described in U.S. Pat. No. 4,238,558 low density magnetic polymer carrier materials containing a polymer material impregnated with a magnetic elemental metal or metal oxide of a transition metal carbonyl. According to the disclosure of this patent, the carrier particles are prepared by placing in a suitable vessel particles of the polymer material, a suspending medium, and a transition metal carbonyl, heating the mixture with agitation for the purpose of thermally decomposing the transition metal carbonyl causing the polymer to be impregnated with the magnetic elemental metal or metal oxide of a transition metal carbonyl, followed by cooling.
Moreover, there is disclosed in U.S. Pat. No. 4,150,173 a process for preparing transparent colored magnetic materials by for example, heating a mixture of a silicaceous material, a suspending medium, and a transition metal carbonyl, wherein the silaceous material is coated with the magnetic elemental metal of the transition metal carbonyl.
While the above described developing compositions are useful for their intended purposes, there continues to be a need for improved color developer compositions. Additionally there is a need for transparent single component developer compositions which have magentic properties. Additionally there is a need for developer compositions having high magnetic strength and excellent color saturation. Furthermore, there continues to be a need for developer compositions having high magnetic strength and excellent color saturation that are fusible or otherwise fixable to appropriate substrates such as paper.